In general, an optical disc recording apparatus that performs recording on a writable optical disc performs, in advance to recording, a step of obtaining the optimum recording power through calibration (hereinafter, referred to as OPC: optimum power calibration) in order to optimize a laser power for recording. In a case where the optical disc is rewritable, the optical disc recording apparatus shifts the optical head to the power calibration area, which is a rewritable area provided on the disc in advance, and executes the OPC thereon.
Typically, the number of recording unit blocks (RUBs) used in the OPC is set to a predetermined number in advance. A destination of the optical head for initiating the OPC may be set to any place in the power calibration area if a predetermined number of RUBs can be continuously obtained. That is, the start address of the OPC may be set to any place in the power calibration area as long as a predetermined number of RUBs can be continuously obtained. However, this is based on the assumption that the optical disc recording apparatus has only a single optical head.
The optical disc recording apparatus performs the OPC as a calibration process for optimizing laser emission power in the writing thereof before the write process. The OPC is controlled by the system controller. A basic OPC sequence is as follows.
(1) The write operation is performed only for a predetermined number of RUBs corresponding to the OPC start address designated by the system controller with the OPC evaluation power.
(2) The written portion is read.
(3) The system controller computes the optimum write power based on the amplitude of the read RE signal. In addition, OPC convergence is assumed when the optimum write power is found. For example, JP-A-2009-301634 discloses a technique of more easily improving stability of the OPC convergence value.